Objective: To compare the biomechanical performance of adjunctive locking plating and double-loop cerclage wiring in feline femora implanted with Zurich cementless total hip replacement (THR) stems.
Study design: Cadaveric biomechanical study.
Animals: Paired femora (n = 32) from 16 feline cadavers.
Methods: Two sequential studies were performed. First, femora implanted with Zurich cementless stems alone were compared with those stabilized by an adjunctive locking plate. Second, femora with locking plates were compared with those with cerclage wires. Constructs underwent cyclic axial and torsional loading followed by load-to-failure testing. Outcome measures included residual axial and torsional displacement, yield and ultimate forces and torques, energy absorption, and brittle failure frequency. Parameters were normalized to bone volume.
Results: The locking plate group demonstrated substantially reduced residual torsional displacement and a trend toward lower axial displacement compared with the stem-only group. Yield and ultimate failure strength did not differ. The cerclage group exhibited 36% greater ultimate axial displacement, 76% greater energy absorption, and 32% greater torsional displacement than the locking plate group. Normalization accentuated these differences. Cerclage wire fixation was associated with a lower frequency of brittle failure.
Conclusion: Locking plates improved cyclic stability by reducing micromotion, while cerclage wires enhanced compliance and energy absorption under destructive loading. Neither method increased load to failure.
Clinical significance: Adjunctive plate or cerclage wire provided biomechanical advantages in femora implanted with Zurich cementless THR stems. Locking plates may support implant stability, whereas cerclage wiring improves energy dissipation under supraphysiologic loading. Adjunctive fixation strategies should be tailored to patient-specific femoral morphology and fracture risk in feline THR.
